The invention relates generally to indication systems for cable leads, and more particularly to identification systems that enable the signal strength or quality for cable leads to be visually represented on the cable leads during studies or monitoring of patients.
Electrocardiography (ECG) studies record the electrical activity and pathways of a heart to identify, measure and diagnose arrhythmias. In particular, such studies measure electrical changes caused by the depolarization of the heart muscle during each heartbeat. To accomplish this, ECGs utilize electrodes that are combined into combinations, the output of which are referred to as a lead.
ECG leads are used in electrophysiology (EP) studies, which assess electrical activity through the use of catheters placed in the heart through veins or arteries. More specifically, surface ECG leads attached to the patient are used as the reference for the intra cardiac signals from the catheters. That is, they provide a voltage reference to the patient for measurement by other leads.
For EP recorder devices in general there is a strong reliance for the signal formation on the surface leads relative to the Wilson Central terminal. Thus, any degradation in the quality of the signal from the patient from the electrode, through the lead wire, the block and trunk cable can affect the intra-cardiac channels negatively with the imposition of noise on the wanted signal. An important mitigation for this is to ensure good electrode contact thus good signals from the electrode to the EP device.
In this context, ECG leads may encounter noise from a variety of sources such as power lines and wireless electrical devices. Moreover, EP studies are typically combined with ablation therapy in which a catheter employs radiofrequency energy, for example, to treat arrhythmias. Various medical devices may also attached to a patient during an EP study potentially creating noise. In addition, ECG leads have to measure relatively small electrical signals from the patient, less than 20 uV in some instances. As will be appreciated, given the above considerations, achieving acceptable study recordings may be challenging.
One significant problem in the utilization of the ECG in EP studies is physician awareness of the quality of the electrode site relative to the surface leads, and more importantly their impact on the intracardiac lead formation. While error messages on the screen of the monitoring device to which the surface leads are attached are a very logical solution to address this, the physician work space by necessity is already complex. Thus, any warning messages on the monitor screen, and additional demands on the user can be counterproductive.
Further, typically degradation of the electrode site occurs over a long period of time. Whereas loss of contact happens quickly, i.e., a bad lead, or disconnect from the electrode tab, which can be readily apparent either on the patient (disconnect) or on the monitor (warning of loss of signal from bad lead) intermittent signal behavior is not as readily noticeable and can easily be overlooked.
In addition, this challenge increases exponentially with complex patient studies such as performed in cardiac electrophysiology where catheter/lead sets of up to 250+ individual catheters/leads are possible, such as when using complex mapping catheters. In these situations, it is often difficult to locate a non-functional or reduced functioning lead which can cause significant issues, including a misdiagnosis of the patient.
There are many pre-existing solutions to electrode quality determination such as PCT Application No. WO/2008/056309A3, entitled ECG Electrode Contact Quality Measurement System. However, while references of this type can determine the quality of the signal received by the electrode, the manner in which these determinations are conveyed to the physician remain the same, i.e., a warning or error message on an EP recorder screen, which is often lost in the midst of all other information being displayed on the screen, or an audible alert, which can often be thought or as distracting and can be lost in other sounds provided by the EP recorded or other devices within the area in which the procedure is being performed. As such, any conveyance of an error message related to the signal quality needs to be done in a more direct and readily-assimilated manner.
In one prior art attempt to solve this issue, U.S. Pat. No. 5,042,498, entitled Intelligent Electrocardiogram System, which is expressly incorporated herein by reference in its entirety for all purposes, discloses an electrode for use with an ECG system or instrument that includes an LED incorporated within the electrode structure. The LED is operably connected to the device, such that when a difference in the impedance between the patient and the electrode is detected, the system activates the LED to identify the faulty electrode.
While capable of identifying the particular electrode that is malfunctioning, the LED utilized on this electrode provides only rudimentary information concerning the electrode function, and nothing concerning the quality of the cable lead or the signal from the patient being transmitted via the cable lead.
Accordingly, it is desirable to develop a visual indication system and method for the indication of the quality of a signal from an ECG lead at the patient, with the indication providing visual information regarding the signal as well as changes in the signal during the study utilizing the indication system.